The aim of our research project is to find out whether the Duplex Theory of Sound Localization--binaural time and intensity differences in auditory stimulation furnish the cues for accurate directional hearing--is adequate to account for the recent data that have been emerging. We plan to investigate the influence of monaural spectral cues on binaural localization. We will approach the problem in three ways: (1) Fill the pinnae contours with malleable substances, thereby confounding the spectral cues provided by the pinnae, and see whether direction hearing under binaural listening conditions is impaired. (2) Require binaural listeners to locate narrow bands of noise which differ one from another, in center frequency. We know that when listening monaurally, the apparent location of these stimuli depends on their frequency composition. We will discover the extent to which this phenomenon is expressed when listening binaurally. (3) Notch out certain frequency bands important for monaural directional hearing and find out whether the presence of these bands promote proficiency in binaural localization.